Eirene
Diagnostic description:
Hydroids colonial, stolonal or erect. Hydrothecae pedicellate, often reduced to a collar below hydranth. Hydranths extensile, tentacles with a distinct basal web of tentacles, hypostome dome-shaped, nematothecae absent. Gonophores free medusae; gonothecae pedicellate, club-shaped with very thin perisarc, arising from hydrorhiza or pedicel adjacent to hydranth. Fully developed medusae without lateral or marginal cirri, with numerous closed marginal vesicles, tentacles lacking abaxial longitudinal groove.